Oscillograph galvanometer



June 10, 1930. J. w. LEGG OSCILLOGRAPH GALVANOMETER ori inai Filed Nov.26, 1924 INVENTOR .roseph/l/Legg'.

ATTORNEY Patented June 10, 1930 PATENT; OFFICE UNITED STATES JOSEPH W.LEGG, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC &MANUFACTURING COMPANY, A CORPORATION OF IENNSYLVANIA OSCILLOGRAPHGALVANOMETER Original applicationflied November as, 1924, Serial No.752,427. Divided and this application filed September 18, 1928.

My invention relates to oscillographs or oscilloscopes and particularlyto those of the 1 portable type in which the characteristic of anelectrical quantity may be observed by viewing an effect produced by thevibrations of the deflecting system of the instrument as the quantity isimpressed upon it.

An object of my invention is to provide a device of the above-mentionedcharacter that shall employ a single galvanometer element and meanswhereby the same may give ap,

parently simultaneous indications of conditions in different circuits orof different conditions in the same circuit.

Another object of my invention is to reduce the size and Weight of aportable oscillograph or oscilloscope and to render the same simple,compact and durable in construction,

economical to. manufacture and effective in operation.

Heretofore, in oscillographs or oscilloscopes in which photographiccharts or polygons of mirrors have been employed for obtaining curves ofthe instantaneous values of the voltage, current and othercharacteristics of electric circuits, it has been usual. to employ anumber of galvanometer elements corresponding to the number of circuitsor characteristics to be simultaneously studied. This practice naturallyresulted in the production and use of instruments of relatively largesize and cost.

In practicing my invention, I provide a galvanometer element, a polygonof viewing mirrors and a switching means for so rapidly changing thegalvanometer element from one circuit to another that the persistency ofhuman vision causes the elements to' appear to give simultaneousindications of the quantity being measured in each circuit.

, This application is a division of my copending application Serial No.7 52,427 filed November 26, 1924.

Other features and advantages of my invention will appear fromthefollowingdescription, taken in connection with the accompanying drawing,in which,"

Figurel is a view partly n side elevation,

bodying my invention; and

Serial No. 305,857.

Fig. 2 is a circuit diagram of the electrical connections employed.

Referring to Fig. 1, the oscillograph comprises a casing 1, agalvanometer 2, a lamp 3, a light shield 4, a prism 5, a lens 6, apolygon of viewing mirrors 7 and a commutator 8.

The casing 1 is preferably constructed of a sheet-insulating material,such as fibrous material impregnated with a binder, and comprises a baseplate 9, an end plate 10, side panels 11, a horizontal partition plate12 and a single integral sheet-13 constituting the top and rear wall ofthe casing.

' The top and rear wall portions of the casing are joined by a portionof gradual curvature for facility of manufacture, and are integral tomake the casing light-tight and so of which is described in myco-pending application, Serial No. 757,586, filed December 23, 1924,compri'les a fluid-tight casing 17, disposed irr the lower rear portionof the casing 1 containing a horizontally disposed galvanometer mirror14 arranged beneath the lens or window 18 in the upper wall portion ofthe galvanometer casing. Terminals 19 are provided for'this galvanometerwinding, and a structure 20 is provided for the purpose of "admitting afluid to the galvanometer casing and for adjusting the tension on thegalvanometer element, as set forth in the co-pending application.

The lamp 3 is'adjustably mounted on one of the side panels 11, andcomprises an elongated filament constituting a linear light source forthe galvanometer 2.. The light shield 4, preferably constructed ofrelatively thin sheet aluminum, is of substantially funnel shapeandrectangular in horizontal section. The shield is secured, at itslarger end, to the horizontalpartition 12 surrounding an opening 21 inthe latter. The shield 4 affords a passage enclosing a portion of thelight beam reflected from the mirror 14, as indicated by the broken line22, and projects 10o I downwardly from the partition 12 so that thelower end thereof is ust above the galvanometer 2 and beneath the lamp3. This construc: tion prevents stray light beams from the lamp fromentering the passage defined by the shield 4.

The prism 5 secured in position on the partition 12 over the opening 21directs the beam from the mirror 14 through a semi-cylindrical lens 6toward a slot 23 in the end plate 10 The lens 6 is clamped to a member24 that is adjustably mounted on the partitions12 by means of a screw 25which extends through a slot 26 in the partition 12. This constructionpermits the beam to be properly focused, through the slot 23, upon aground-glass screen 27 so that it can be viewed in the polygon ofmirrors 7.

A member 28 of substantially U-shape,

preferably constructed of sheet or strap material, is held inslightly-spaced parallelplane relation to the outer surface of the endplate 10 by a spacer 29; .The arrangement of parts permits the flangedplates 30, supporting the polygon of mirrors 7, to be slipped intoposition behind the membe1-28 to hold the mirrors in proper relation tothe slot 23. The polygon-of-mirrors device comprises four mirrors 31mounted on a shaft 32 which is journalled in the flanged plates 30, andwhich carries a pulley 33 on one end thereof and a commutator 8 on theother end. Brushes 34 are mounted on one of the flanged plates 30 sodisposed that they cooperate with the commutator 8.

The polygon of mirrors 7 is rotated at a high rate of speed by a beltconnecting the pulley 33 to a motor (not shown)2 Referring to Fig. 2, itwill be noted that the commutator 8 comprises an insulating segment 35and a conducting segment 36 shaped to alternately shift the electricalconnections of the galvanometer element 37 from one circuit to another.The middle brush 34 makes continuous contact with the conducting segment36 while the outside brushes alternately make contact with theconducting segment. In this instance, which is merely illustrative ofone of several sets of circuit shifts which may be effected, thecommutator 8, when rotated, alternately shifts the connection of thegalvanometer element 37 so that the element is energized, at oneinstant, in accordance with the current traversing a circuit 38 and isenergized at the next instant in accordance with the voltage of the samecircuit. The circuit is representative of a usual circuit comprising agenerator 39, a current shunt- 40 and a load device 41. g

With the commutator in the position shown in Fig. 2, the galvanometerelement 37 is connected across the circuit 38 through a conductor 42,resistor sections 43, a conductor 44, the right-hand brush 34, throughthe conducting segment36,the middle brush,resistor sections 45 and theconductor 46. Thereafter, the galvanometer element 37 is connectedacross the current shunt 40 through the conductor 46, certain of theresistor sections 45, the middle brush, the conducting segment 36, theleft hand brush and the conductor 47.

A resistor element 48 is connected from the right-hand brush to theupper terminal of the galvanometer element 37, so that when element 37is energized, in accordance with the voltage of the circuit 38, aportion of the current will be shunted around the right-hand and middlebrushes to prevent sparking of the commutator. In case the oscillographis connected to a low-voltage circuit, there will be no danger ofsparking of the commutator, and the connection from the right-hand brushto the galvanometer element, through the resistance 48, may be omitted.

I The current through the galvanometer element maybe adjustedvariously,in accordance with the character of the circuit 38, by properselection ofthe resistor sections 43 and 45. When the mirrors 31 andcommutator 8 are rotated at, or above a certain speed, the galvanometerelement 37 is shifted from one circuit to the other so rapidly that,because of the persistency of human vision, when one looks down upon theviewing mirrors the current and voltage waves of the circuit 38 appearto be simultaneously present and superimposed.

While the arrangement of parts contained in the casing 1 isthe preferredform for use in connection with the above described circuit, many otherarrangements may obviously be resorted to.

Various modifications may be made in my invention Without departing fromthe spirit and scope thereof, and I desire, therefore, that only suchlimitations shall be placed therein as are shown by the prior art andset forth in the appended claims.

I claim as my invention:

1. The combination with a single electroresponsive indicating means anda plurality of circuits, of means for changing said indicating meansfrom circuit to circuit and for causing the indicating means to effectappar- 1 of means for changing said indimultaneously changing theresistance between said indicating means and said circuits and forcausing the indicating means to eflect apparently concurrent indicationsof quantities of said circuits.

l. The combination with means for passing a beam of energy along apredetermined path, of means for vibrating'said beam of energy inaccordance with a varying electrical quantity, and means for making saidvibrating beam of energy appear as a plurality of waves.

5. The combination with a single electrorespon'sive indicating means anda plurality of circuits, of means for changing said indicating meansfrom circuit to circuit and sin'iultaneously adjusting said indicatingmeans to the several circuits and for causing the indicating means toeffect apparently concurrent indications of quantities of said circuitsin superimposed relation.

6. In combination with a single deflecting element and a polygon ofviewing mirrors, means including a commutator for switching said elementfrom one circuit to another ata rate at least equal to the persistencyof human vision.

7. In combination with a single galvanometer-deflecting element and apolygon of viewing mirrors, means including a commutator mounted on theaxis of said polygon of viewing mirrors for switching said element fromone circuit to another at a rate at least equal to the persistency ofhuman vision.

8. In the art of obtaining plural indications from a singlegalvanoineter deflecting system, the step which consists inapparentlysimultaneously producing upon a viewing surface a plurality of curvesgenerated by light beams emanating from said deflecting system. l

9. In the art of obtaining plural indications from a single galvanometerdeflecting system, the step which consists in apparently simultaneouslyproducing upon a viewing surface and in superposed relation apluralitypf curves generated by light beams emanating from saiddeflecting ystem.

10. The method of operating apparatus including a deflecting element anda viewing ineans which comprises switching said elementfrom one circuitto another at a speed at least as great as the persistency of humanvision. 1

11. In combination, a light-reflecting galvanometer element, a tubularlight-shield through which light from the element is reflccted and whichhas one end disposed adj acent to the element, and a source of lightdisposed outside the'tubular shield farther from the element than theadjacent end of the shield.

12. The combination with a casing having a partition dividing the sameinto upper and lower compartments, of a galvanometer incl uding alight-reflecting element in the lowor compartment, light-reflectingmeans d1s-' posed ad acent to an opening in said partition, a tubularlight shield for directing reflected light from a position adjacent tosaid. element. through said opening and said light reflecting means,and. a lamp disposed outside said shield above the lower end thereof.

In combination, a substantially'rectangular casing, a light-transmittinggalvanometer element disposed adjacent to the lower rear-end portiontherein, a light-transmitting opening in the upper front wall of thecasing and a prism adjacent to the upper rear portion in the casing fordirecting a light beam from the element to the opening, the top and rearwalls of the casing being integrally connected.

14, In combination, a substantially rectangular casing, alight-transmitting gal'vanometer element disposed adjacent to' the lowerrear-end portion therein,a light-transmitting opening in the upper frontwall of the casing and a prism adjacent to the upper rear por' tion inthe casing for directing a light beam from the element to the opening,the top and rear walls of the casing being formed of a single sheetmember.

15. In combination, a substantially rectangular casing, alight-transmitting galvanometer element disposed adjacent to the lowerrear-end portion therein, a ting opening in the upper front wall of thecasing and a prism adjacent to the upper rear portion in the casing fordirecting a light beam from the element to the opening, the top and rearwalls of the casing being formed of a single sheet member having acurved portion between the intersecting top and rear-Wall portions.

16. A system comprlsing means for passing a beam-of energy along apredetermined path,

a viewing means, means including a single 111821115, means including asingle galvanometer-deflecting element for reflecting said beam to saidviewingmeans and for vibrating it in accordance with ,a' varyingelectrical quantity, and means for switching said element from one ofsaid circuits to another of said circuits at a rate at least equal tothe persistency of'human vision.

18. A system comprising a cuits, means for passing it along apredetermined path, a polygon of viewing mirrors, means including asingle galvanometer-deflecting element forreflectlight-transmitplurality of cirbeam of energy ingsaid beam to saidviewing mirrors and for .vibrating it in accordance with a varyingelectrical quantity, and means for switching said element from one ofsaid circuits to another of said circuits at a rate at least equal tothe persistency of human vision.

19. In combination,astraight-line source of light for supplyinga band oflight, means including a galvanometer-deflecting element for vibratingsaid band of light in accordance with the variations of an electricalquantity, the axis of vibration of said galvanometer element and theaxis of said straight-line source being in the same plane, a reflectingsurface positioned in the path of said band of light substantiallyerpendicular t0 the plane of said band of fight, an indicating surfacein the path of said reflected band, and a cylindrical condensing lenspositioned between said indicating surface and said reflecting surface.

In testimony whereof, I have hereunto subscribed my name this 7th day ofSeptenr ber, 1928.

JOSEPH W. LEGG.

